MyBB Community Forums

I new for MyBB.
Now My Forum version is 1.8.11.  
How I upgrade to 1.8.13????

please see upgrading guidance

How to update to 1.8.13?

1. put forum offline & take backup of the database.
2. upload files of the new version by overwriting existing files
3. visit [your forum url]/install/upgrade.php on your web browser & follow the instructions you get on screen

4a. check for the updated templates after the upgrade process completes

4b. see also this css style codes update related post